Many people owe their lives to specially trained diabetic alert dogs that can detect blood-sugar fluctuations before the patient can.

Rebecca Farrar was just 4 years old when she became seriously ill and was diagnosed with diabetes. Today, as a Type 1 diabetic, 8-year-old Rebecca’s blood sugar can drop without warning, putting her at risk of hypoglycemia, which can lead to a coma or even death.

Dogs have provided assistance for people with physical and mental disabilities for decades, but in recent years researchers have discovered that canines can also detect illness in humans. With a sense of smell 100,000 times more sensitive than ours, dogs have sniffed out many things, including cancer and dips in glucose levels.

Originally, Rebecca’s dog was being trained in the U.K. as a seeing-eye dog, but she had to replaced because she didn’t like her harness. However, her diabetic owner had noticed that she always licked his hand before he became hypoglycemic, so Shirley was retrained as a diabetic alert dog.

Today, Shirley licks Rebecca’s hand when her blood sugar begins to drop. If Rebecca doesn’t respond, the dog will get the attention of another family member, often bringing Rebecca’s sugar-testing kit with her.

Almost 350 million people have diabetes worldwide, according to the World Health Organization. However, it can be difficult for Type 1 diabetics — many who have lived with fluctuating blood sugar levels all their lives — to tell when their blood sugar is out of balance. The early warning that a dog can provide can save their lives.

Dan Warren, a Type 1 diabetic and retired U.S. Marine who used to train bomb-sniffing dogs, runs Warren Retrievers, an organization located in Orange, Va., that trains diabetic alert dogs. His dogs learn to warn diabetics of potential problems, to retrieve shot kits and food, and even to call 911 in an emergency.

He says that dogs can detect the onset of seizures 20 minutes or more in advance and can sense blood-sugar fluctuations up to 45 minutes beforehand.

"In a glass of iced tea, we can smell a teaspoon of sugar," Warren told the Gaston Gazette. "Dogs could smell that teaspoon of sugar in an Olympic-size swimming pool."

"They can see and smell all sorts of things we don’t," Dr. Lawrence Myers, an expert in canine scent detection at Auburn University College of Veterinary Medicine, told WebMD. However, he says there’s "a lack of reliable data that confirms that they are doing that, and doing that reliably."

Despite the lack of conclusive scientific evidence, Robby and Melissa Putnam say that their diabetic son’s dog, Scout, gives them peace of mind.

One in 20 Type 1 diabetics die in their sleep after blood glucose plummets, so 12-year-old Josh Putnam gets up at 3 a.m. every day to check his blood sugar levels.

"Scout is a huge relief," Josh’s mom, Melissa, told the Gaston Gazette. "You look down and see that she’s nice and calm. You know he’s good."